The most common types of light bulbs are incandescent, compact fluorescent lamp (CFL), and light emitting diode (LED). The incandescent light bulb design concept is a vacuum globe enclosing a conductive filament wire which glows when a current passes through. A CFL is shaped into a size similar to incandescent bulbs with a mercury vapor filled tube of glass excited by electricity, producing short-wave ultraviolet light through a phosphor coating which fluoresces to emit visible light. An LED bulb typically consists of several LED lamps grouped together to adjust light intensity, direction, color, or voltage. An LED bulb may be enclosed by glass or plastic resembling an incandescent bulb. Dimmable LED bulbs are available, but their cost may be prohibitive. Recent developments in both CFL and LED bulbs have allowed replacement of many incandescent bulbs by increasing life span and power efficiency.
Homes and businesses use multiple light bulbs or fixtures for general light and additionally may have a separate dedicated source when low intensity light is desired. Low intensity light is often used to provide enough light for people to see when traversing in the dark or to alleviate fear of the dark. While general light is usually implemented as a permanent ceiling, wall, or furniture fixture, low intensity light is typically implemented as a removable wall-mounted fixture referred to as a nightlight. Nightlights may be plugged into electrical receptacles in rooms, hallways, or entryways. Having separate solutions for general and low intensity light has a number of limitations. Separate implementation requires an excessive number of light fixtures. Low intensity light is less efficiently distributed through the area. Receptacles may not be available where needed, and receptacles are no longer available due to use by a nightlight. Electrical dangers for children are also a concern of separate low intensity light fixtures, due to low height and ease of removal.
Fragrance and sound generators improve the atmosphere of a room. Particularly at night, sleep can be enhanced when background noise or fragrance is emitted. Like nightlights they are also often wall-mounted fixtures and have similar drawbacks.